The 3G (3rd Generation, 3rd Generation Mobile Communication System) signaling network is an important supporting network for 3G service network, and the all-IP (Internet Protocol) network represents a development trend of mobile communication. For example, WCDMA introduces an idea of soft switch to separate call control from bearer control. A MSC (Mobile Switch Center) may be divided into a MSC SERVER of the control layer and a MGW (Media Gateway) of the bearer layer.
A new signaling system is needed to support the separation of the control layer and the bearer layer. Since the control layer is only in charge of voice service, there are mainly two demands on this layer: the first is that the MSC SERVER must be able to control the remote MGW, because the MSC SERVER and the MGW may be at different locations, even in different cities. The second is that the MSC SERVERS can switch information between each other, so as to establish an end-to-end call. The conventional signaling system cannot satisfy the above-mentioned demands.
The evolution of the network towards an all-IP network is a progressive process. The future 3G signaling network will face an interworking problem between the circuit-switched-based No. 7 signaling and the IP-network-based signaling in a relatively long period of time.
An important concept used in interworking is signaling transport. In an interworking process between a narrowband signaling network and a broadband signaling network, when the interworking is implemented through M3UA (Message Transfer Part 3 User Adaptation Layer), it is a technical problem to be solved as to how to forward a TFP (TransFer Prohibited) message received from the narrowband signaling network to ensure the reliable operation of the network. In an implementation of the conventional narrowband signaling network, on receiving a TFP message whose destination signaling point is not the local office signaling point, the TFP message will be forwarded. No problem will occur in the narrowband network because there is no change in the message format during the forwarding. But at the interworking point SG (Signaling Gateway) between the broadband network and the narrowband network, on receiving a TFP message whose destination signaling point is not the local office signaling point, the TFP message needs to be transparently transported to the opposite end according to the processing in the narrowband network since this TFP message is not a message to be processed by the local office, that is, the TFP message will be transparently transported to the broadband signaling point through an M3UA message for processing.
In the above-mentioned method for transparently transporting the TFP message, it can be seen that,
Firstly, the broadband signaling point has to have a part of functions of the MTP3 to be able to process the route management messages of MTP3. This is somewhat inconformable with the way of implementing adaptation function by M3UA protocol.
Secondly, with the above-mentioned method, the SG simply implements a transparent transport of route management message without performing any route analysis function, so that the SG's function of interworking between the broadband network and the narrowband network is not fully utilized.